An electrical characteristics inspection of an object to be inspected such as a semiconductor wafer or the like is performed by, e.g., taking tip images of a plurality of probes provided in a probe card by a camera, detecting tip positions of the probes and contacting the probes with electrode pads of the object to be inspected. When detecting the tip positions of the probes with a camera, it takes time to focus the camera on the tip of the probe. As a result, much time is spent to align the object to be inspected and the probe card. For this reason, the alignment is not performed for all of the probes in usual cases but performed by, e.g., selecting several representative probes.
In case of the electrode pads being of a fine-size, however, there is a possibility that the probes may fail to make close contact with the respective electrode pads in their entirety. Therefore, it is desirable to detect the tip positions of all of the probes as far as possible. Further, the probe card suffers from variations in production quality, which variations are seldom avoidable even if the probe cards are of the same specification. This makes it necessary to detect the tips of the probes in more precise manner.
Further, since various kinds of probe cards are developed by different probe card makers, there is a need to develop card-specific algorithms for recognizing three-dimensional image of a plurality of probes. However, huge costs are incurred in developing the card-specific algorithms for the three-dimensional image. Therefore, by transferring the probes to a two-dimensional film, it is possible to develop the algorithms with ease.
For example, Japanese Patent Publication No. H5-067059 (JP-B-H5-067059) discloses a probing method for aligning probes and a wafer. In this method, the probe marks of probes are transferred to a wafer aligned on a table or a sheet attached to the table. The orientation of the wafer is compared with the orientation of the probes. The orientation of the table is corrected according to the result of comparison, whereby, the XY coordinates of a reference chip of the wafer are brought into coincidence with the XY coordinates of the probes.
Japanese Patent Laid-open Application No. 2005-079253 (JP-A-2005-079253) discloses a method for detecting a tip status of probes by using a transfer sheet. In this method, probe marks are left by bringing heat-expanded probes into pressure contact with a transfer sheet arranged in a transverse support base of a mounting table. After detecting the probe marks left in the transfer sheet, the heat-expanded probes are aligned in position with the wafer.
Japanese Patent Laid-open Application No. H2-224260 (JP-A-H2-224260) describes a position aligning method in which the direction and position of probes are recognized by leaving probe marks of probes in a dummy wafer and detecting the probe marks with a camera.
However, JP-B-H5-067059 has no description about the detection of tips of probes which is one of important alignment factors. In case of JP-A-2005-079253, the XY coordinate data of the probes are acquired by using the probe marks of the probes left in the transfer sheet. In order to detect the height of the tips, however, it is necessary to detect the depth of the probe marks, which makes it difficult to find the height of the needle points with increased precision. In case of JP-A-H2-224260, the tip positions of the probes are found by using the probe marks left in the dummy wafer. Therefore, it is possible to acquire the XY coordinate data of tips as in JP-A-2005-079253, but the Z coordinate data of tips is obtained by a camera with no alternative method.